Whether it is possible for anything to exist without structure is an interesting question. Is there an example of such a thing? Maybe someone who understands math better than I do can say whether the empty set has structure (or maybe it is structure).

But anything made by a conscious act of will of a sentient being (like human music, defined any way and from any place or time) involves creative choices and thus has structure.

I know thats a very broad statement and it only applies to my limited knowledge of classical music and what I consider to be 'good' ambient.

I think the distinction between the two is that the ambient to which I'm referring too can create 'new' sonic spaces. What I mean by that is the element of manipulation of sound - so that even acoustic sources can be drastically transformed. The sound becomes amorphous. I get a sense of the mysterious and the ethereal from some ambient, which I don't get from classical.

Structure is an entirely different matter, as is tempo, how does a drone have tempo ? 'Play very very slowly with feeling'

I can't see a link between the electronic textures in ambient and any kind of instrumentation in classical, or the use of field recordings, vocal samples, glitch etc.

Oh - and drones - at least the interesting ones to me have modulation to them in some manner or another so still have a "beat" in the sense that there is a subtle inherent rhythm to the drone - even if it's hyper slow.

Oh - and drones - at least the interesting ones to me have modulation to them in some manner or another so still have a "beat" in the sense that there is a subtle inherent rhythm to the drone - even if it's hyper slow.

I guess for that matter, any sound has a rhythm to it because it is a wave.

Ambient music is not all formless. Some is, some isn't. Also, formless is a very over-used and oft mis-interpreted word in ambient circles. I think people sometimes say formless when they are referring to texture: a gassy vaporous type sound does not mean formless, in the traditional musical sense. The correct usage of the word formless refers to the lack of sections within a piece (as in verse chorus verse or ABA etc). A formless piece may simply have an A section, and as I said, some are formless, but many are not. Just clearing that one up there.

Even John Cage's 4m 33s has structure, in that the pianist opens and closes the piano lid to signify the different movements. Though the idea of forcing an audience to listen to the sounds around them is perhaps as formless and ambient as can be created....

Perhaps white noise could be described as formless - but then perhaps hearing only certain frequencies also gives it structure.

To me where 'ambient' and 'classical' can overlap, it is in the choices of sounds to create a space that is not dependent upon timing, meter or verses etc.

As I mentioned before, some of the very early choral musics are very similar to floaty ambient pieces. shift the frequencies of the voices down to bass drones and it would be hard to distinguish the two apart. Though this effect is helped by my not understanding the language they are sung in, so it becomes notes and sound rather than notes and words.

Even John Cage's 4m 33s has structure, in that the pianist opens and closes the piano lid to signify the different movements. Though the idea of forcing an audience to listen to the sounds around them is perhaps as formless and ambient as can be created....

As it defines down to the second how long it should be, 4m33s is an extremely structured piece of music. Beethoven never wrote in his scores, "To be performed in the space of one hour and 4 minutes."